This invention relates to an alarm pull station which is typically mounted on the wall of a building to be manually activated in the event of a fire or alarm occurence to transmit a signal to a local alarm and to a remote fire or police station and, more particularly, to such a manually operated pull station which incorporates a Hall effect sensing device.
Red fire alarm pull stations can be seen in schools, office buildings and various institutions. These pull stations typically comprise a red box having a glass panel which must be broken so that a manually operated lever can be depressed in the event of a fire for sounding a bell or other fire alarm device within the building so that it can be evacuated without loss of life and to also provide an alarm signal to a nearby fire station so that fire personnel can respond and minimize the damage to the building as quickly and efficiently as possible.
Such pull stations incorporate a wide variety of mechanical switching devices to sense the operation of the manually operated lever to provide the signal to the local alarm indicator and the signal to the remote fire or police station. Most of the mechanical or magnetic switches of the past have been subject to a myriad of problems. For example, moisture, dust, contact point wear and oxidation and corrosion have, either acting alone or in combination, impaired the operation of the pull station. Such pull stations are not as reliable as might otherwise be desired and have required too much maintence in order to maintain reliability. Moreover, these bulky mechanical arrangements are unnecessarily large resulting in excessive cost and less usefulness.
The present invention, however, incorporates a Hall effect magnetic sensing device in a pull station which operates in response to a magnet moved by a manual operator for providing an alarm signal which can be used by a local alarm indicator for warning the inhabitants of the building in which the pull station is located in the event of a fire and for providing a remote alarm signal to a fire station or police station so that the proper personnel can respond to the alarm occurrence. A pull station incorporating a Hall effect switching device is immune to moisture and dust, has no contact point wear since there are no mechanical contacts, is immune to mechanical contact bouncing since there are no mechanical contacts, involved, is immune to oxidation, tarnishing and corrosion, is substantially explosion proof, reliable, small and requires little maintenance. Moreover, such a device can be easily arranged to provide a normal signal when unactivated, an alarm signal when activated and a trouble signal when there is tampering of the pull station box or housing.